Functional Allocation
Using a functional allocation, we take the key functions identified in the Functional Flow, and aggregates them into a hierarchical tree. The purpose of this process is to ensure that all the required functions of a system are mapped into the subsystems.
Similar tools
Hierarchical breakdowns of system are a common method used in a ‘reductionist’ approach. In this topic we break the functions into the likely subsystems, but there are many other ways that a system could be broken down. For example, a Work Breakdown Structure is a hierarchical map of allocating work between departments or team members.
Steps
Start with the key functions from your FFBD.
- Group the key functions into similar functional groups. Try to make each group as self-contained as possible: this promotes modularity and reduces interdependence of a system
- Look for themes around functional groups, and assign them to an actor, resource or subsystem; for example, electrical system, mechanical system, or control system.
- These units become the building blocks for the functional packaging of your design, and ultimately shape the characteristics of the relationships in your system.
Hints
- Ensure as much as possible that the functions within a group are self-sufficient, requiring as little interaction with other systems as possible. There are, however, trade-offs. For example, a mechanical car lock will operate independently, whereas central locking relies on the electrical system. If your battery fails, then you can be locked out of your car, which can be a good thing if you are trying to keep people out, or a bad thing if you’re trying to get in.
- If you’re considering functional allocation in a work group, there may need to be high duplication in order to make a unit self sufficient. Take, for example, a company with global offices. It might make sense to house all of the IT support in one location, but it might reduce the responsiveness to IT-related problems, driving down productivity. Instead, it might make more sense to distribute the IT support between offices so that each office has the capacity to function. In reality, it might be a combination of centralised and distributed support.